1. Field of the Invention
This invention relates to a combustion chamber for a combustion turbine and more particularly to a step-liner combustion chamber having double wall construction.
2. Description of the Prior Art
Double wall step-liner combustion chambers for combustion turbines are known and have been used in certain turbines manufactured by the assignee corporation of the present invention. Such structure is adequately shown and described in U.S. Pat. No. 3,702,058 and has the design advantage of convectively cooling the chamber by directing cooling air against the hot outer surface of the combustion chamber wall and providing film cooling by directing a layer or film of air on the inner surface of the combustion chamber wall. Although the double wall structure provides these advantages for cooling the chamber, the thermal gradient between the inner and outer walls results in relative thermal growth therein that produces stresses in the assembly that can result in early failure of the chamber. In recent years, the combustion turbine operating temperatures have been increasing, requiring ever-increasing temperatures within the combustion chamber. Such higher temperature chambers would be benefited by the efficient cooling provided by the double wall configuration but further increases to the temperature gradient and the resulting stresses would not be permissible if the chamber were assembled in the manner known in the prior art.